The present invention relates to electric vehicles, and more particularly to an all-electric vehicle system that is powered from an onboard high-specific-power energy storage device, and that receives power to charge the energy-storage device inductively through coils in the roadway over which the vehicle travels. The invention further relates to enhancements included within such a roadway-powered electric vehicle system, such as an automatic position-determining system, automated vehicle guidance, demand-based vehicle dispatch, and the like.
In recent years, there has been an increasing emphasis on the development of an all electric vehicle (EV) or other zero emission vehicle (ZEV). The goal, as mandated by many governmental jurisdictions, is to have a certain percentage of all vehicles be zero-emission vehicles. Advantageously, zero-emission vehicles do not directly emit any exhaust or other gases into the air, and thus do no pollute the atmosphere. In contrast, vehicles that rely upon an internal combustion engine (ICE), in whole or in part, for their power source are continually fouling the air with their exhaust emissions. Such fouling is readily seen by the visible “smog” that hangs over heavily populated urban areas. Zero-emission vehicles are thus viewed as one way to significantly improve the cleanliness of the atmosphere.
In the State of California, for example, the California Air Resources Board (CARB) has mandated that by 1998 two percent of the vehicles lighter than 1700 kg sold by each manufacturer in the state be zero-emission vehicles. This percentage must increase to five percent by the year 2001, and ten percent by the year 2003.
A zero-emission vehicle, given the known, viable technologies for vehicle propulsion, effectively means that such vehicles must be all electric, or electric vehicles (EV's). Hence, if existing (and future) governmental mandates are to be met, there is an urgent need in the art for a viable EV that can operate efficiently and safely.
EV's are not new. They have existed in one form or another since the discovery of electrical batteries and electric motors. In general, EV's of the prior art are of one of two types: (1) those that —through rail or overhead wire—are in constant contact with an external source of electrical power (hereafter “externally-powered” EV's); or (2) those that store electrical energy in a battery and then replenish the stored energy when needed (hereafter “rechargeable battery-driven” EV's).
Externally-powered EV's require their own power delivery system, e.g., electrified rails or electrified overhead wires, that forms an integral part of their own roadway or route network. Examples of externally powered EV's are subways, overhead trolley systems, and electric rails (trains). Such externally-powered EV systems are in widespread use today as public transportation systems in most large metropolitan areas. However, such systems typically require their own highly specialized roadway, or right-of-way, system, as well as the need for an electrical energy source, such as a continuously electrified rail or overhead wire, with which the EV remains in constant contact. These requirements make such systems extremely expensive to acquire, build and maintain. Moreover, such externally-powered EV systems are not able to provide the convenience and range of the ICE automobile (which effectively allows its operator to drive any where there is a reasonable road on which the ICE vehicle can travel). Hence, while externally-powered EV systems, such as subway, trolley, and electric rail systems, have provided (and will continue to provide) a viable public transportation system, there is still a need in the art for a zero-emission vehicle (ZEV) system that offers the flexibility and convenience of the ICE vehicle, and that is able to take advantage of the vast highway and roadway network already in existence used by ICE vehicles.
Rechargeable battery-driven EV's are characterized by having an electrical energy storage device onboard, e.g., one or more conventional electrochemical batteries, from which electrical energy is withdrawn to provide the power to drive the vehicle. When the energy stored in the batteries is depleted, then the batteries are recharged with new energy.
Electrochemical batteries offer the advantage of being easily charged (using an appropriate electrical charging circuit) and readily discharged when powering the vehicle (also using appropriate electrical circuity) without the need for complex mechanical drive trains and gearing systems. Unfortunately, however, such rechargeable battery-driven EV's have not yet proven to be economically viable nor practical. For most vehicle applications, such rechargeable battery-driven EV's have not been able to store sufficient electrical energy to provide the vehicle with adequate range before needing to be recharged, and/or to allow the vehicle to travel at safe highway speeds for a sufficiently long period of time. Disadvantageously, the energy density (i.e., the amount of energy that can be stored per unit volume) of currently-existing electrochemical batteries has been inadequate. That is, when sufficient electrical storage capacity is provided on board the vehicle to provide adequate range, the number of batteries required to provide such storage capacity is prohibitively large, both in volume and weight. Moreover, when such batteries need to be recharged, the time required to fully recharge the batteries is usually a number of hours, not minutes as most vehicle operators are accustomed to when they stop to refill their ICE vehicles with fuel. Further, most currently-existing electrochemical batteries are not suited for numerous, repeated recharges, because such batteries, after a nominal number of recharges, must be replaced with new batteries, thereby significantly adding to the expense of operating the rechargeable battery-driven EV. It is thus evident that what is needed is a rechargeable battery-driven EV that has sufficient energy storage capacity to drive the distances and speeds commonly achieved with ICE vehicles, as well as the ability to be rapidly recharged within a matter of minutes, not hours.
EV systems are known in the art that attempt to combine the best features of the externally-powered EV systems and the rechargeable battery-driven EV systems. For example, rather than use a battery as the energy storage element, it is known in the art to use a mechanically coupled flywheel, i.e., a flywheel that is mechanically coupled to vehicle's drive train, that is rapidly charged up to a fast speed at select locations along a designated route. See, e.g., U.S. Pat. No. 2,589,453 issued to Storsand, where there is illustrated an EV that includes a mechanical flywheel that is recharged via an electrical connection at a charging station.
Further, in U.S. Pat. No. 4,331,225, issued to Bolger, there is shown an EV that has an electrochemical battery as the preferred storage means, and that receives power from a roadway power supply via inductive coupling. An onboard power control system then provides the power to the storage means, and the storage means then supplies power as needed to an electric motor providing motive power for the vehicle. Bolger also indicates that the storage means could be a mechanical flywheel.
In U.S. Pat. No. 4,388,977, issued to Bader, an electric drive mechanism for vehicles is disclosed that uses a pair of electric motors as motive power for the vehicle. A mechanical flywheel is mechanically connected to the drive shaft of one of the electric motors. The vehicle receives power from an overhead power supply, e.g,. trolley lines, and the motor then spools up the mechanical flywheel. The mechanical flywheel is then used to supply power to the motor at locations where there is not an overhead power supply.
In U.S. Pat. No. 5,224,054, issued to Parry, there is shown a bus-type vehicle having a continuously variable gear mechanism that uses a mechanical flywheel as a power source. The mechanical flywheel is periodically charged by an overhead connection to an electrical supply. The flywheel is mechanically linked to the drive shaft of the vehicle.
In the above systems, the mechanical flywheel is used as the energy-storage element because it can be charged, i.e., spooled up, relatively quickly to a sufficiently fast speed. Disadvantageously, however, the use of such mechanical flywheel significantly complicates the drive system of the vehicle, and also significantly adds to the weight of the vehicle, thereby limiting its useful range between charges. Further, the mechanical flywheel operating at fast speeds may present a safety hazard. What is needed, therefore, is an EV that avoids the use of a flywheel mechanically coupled to the vehicle's drive system. Further, what is needed is an EV that can receive electrical energy from an external source to rapidly recharge, within a matter of minutes, an onboard energy storage element. Moreover, what is needed is such an EV wherein the onboard energy storage element, once charged or recharged, stores sufficient energy to provide the motive force needed to safely drive the vehicle at conventional driving speeds and distances.